Previously known is, among others, a suction valve from U.S. Pat. No. 6,695,007, where the suction flow of the medium to the compressor keeps the valve open. When the flow reduces, or for instance, when the suction effect of the compressor lessens, the spring in the valve pulls the closing means against the seat surface and closes the valve. In such a spring-return valve, a little more suction pressure loss always builds up over time, but because of the suction flow, the valve-closing means is kept open. However, pressure loss builds up further, even if the spring would be, as to its counter force, quite weak. When rather big compressors are working almost day and night, so that there is a slight deterioration in the operating efficiency, and because of the noted suction valve with a weak spring, the suction valve becomes a large expense in the production of compressed air. In addition, it is difficult to regulate a suction valve returning by spring force into an intermediate position near the closing state in order to achieve the relief state of compressor. Thus, the deterioration occurs, the relief which must be done relative to closing of the valve, while the compressor is working, is either adding a spring back factor or otherwise moving the closing means with less force against the closing surface.